95 e320 will not start after head gasket replacement.

[JBS]

I just replaced the head gasket on my 1995 E320. The old gasket failed after 255,000 miles and pressurized the cooling system. I did not notice until there was a loss of power and pinging. The engine then shut off.

I had he head resurfaced.

Since replacing the gasket the car will not start. It spins normally and speeds up slightly when given gas during the cranking process but will not start.

I removed the valve cover and double-checked the timing which appeared correct. (Done at TDC with camshaft dowel holes aligned with top of head surface and intake cam gear rotated clockwise.)

I tested the spark by removing the #1 spark plug and grounding it while cranking. There is spark.

I do not smell fuel as you would expect from flooding after prolonged cranking.

I will perform a compression test tonight and post the results.

Any help would be most appreciated!

[J. M. van Swaay]

Is the wiring harness original?

[JBS]

No, I replaced it with the non-biodegradeable version about two years ago.

[JBS]

This morning I ran a compression test. Not good.None of the cylinders were up to specs. As I mentioned I had the head re-surfaced. Maybe I burned out the rings? I am also going to check the head bolts to see if their stretched.

Any other thoughts???

[mpolli]

Have you ever done a head gasket before? Is that a straight 6 or V6? Unfortunately I am not familiar with that car. Do you know what the compression was before? What readings did you get?

Do not lose "situational awareness". What this means is do not get so preoccupied with one particular question that you lose sight of other more obvious things.

Mike

[JBS]

Hi Mike.
Yes, I have performed a head gasket change before. It is a straight 6. I cleaned the head bolt holes to remove any trapped engine oil and to not damage the block when re-torquing the bolts.

I followed the three stage torquing procedure on the head bolts. (55 Nm, 1st 90 degree, 2nd 90 degree.

I removed the head again just now to inspect. I did notice that the head bolts did not seem that tight. At least not as tight as they seemed when i was wrestling with the torque wrench for the 2nd 90 degree tightening!

[JBS]

All of the bolts are between 161 and 162 mm in length. Spec. is new @ 160 and 163.5 mm Max.

[JBS]

Found it! Burned valves. I put the head back on and pressurized the cylinders while on TDC. Intrestingly coming from the intake valves, not the exhaust. Another trip to the machine shop!

[mpolli]

I would think you or the shop would have noticed that by now.

Mike

[mpolli]

You pressurised all the cylinders while on TDC? Some of the cylinders will have their intake valves open at TDC. And some exhaust etc.

MP

[t walgamuth]

I was thinking valve timing might be off. This will result in low compression if the valves open before or after they should. If off too far the pistons will hit the valves, probably.

If it is a fuel fault it should run on a little ether if all else is correct.

It it is advanced or retarded ignition timing it should backfire or try to fire against the compression stroke.

Tom W

[JBS]

Each cylinder was at TDC when I performed the test. 0 degrees for 1 & 6, 120, and 240 degrees.........
Again, the engine is timed correctly and I can visually determine by looking at the camshaft for the tested cylinder that the lobes of the camshaft are not pushing down on the valves.

I did not notice any issue with the valves as I did not perform a pressure test while removing the head. Would it not be somewhat pointless to perform a leak down test on a head when you know the intake gasket is blown and venting through the cooling system? Also, the leaks are small enough that you cannot see any problem with the valves visually.

I should have performed the leak down test during the rebuild and I would have detected the problem before getting it back together. I did manage to go from a completly assembled engine to having the head off again in 1.25 hours!

I did not ask the shop to pressure test the head. I talked to the owner of the shop today and he asked why it had not been more thoroughly inspected? He was disappointed that his helper that decked the head did not suggest it.

[jhodg5ck]

I'm just surprised you didn't have a valve job done while the head was off..Especially @ that high a mileage.

Does this shop specialize in Mercedes machining? If not I'd find someplace else to have it done.

Jonathan

[brewtoo]

The leaks are so small you cannot see any problem when looking at the valves?

I don't think that would keep the engine from starting.

[mpolli]

That is what I am thinking. Even though they are not perfect I don't think they would result in very low pressure readings (you never did say how low) and I don't think that is the cause of no start. IMHO.

Mike